I've read the same thing - but usually about F-H BP beasts no longer in production. The 29mm Estes E-F BP motors seem to get fewer reports than the 24mm Es. Maybe because fewer are flown - but we can't tell that from public data. Some stories told about motor vulnerabilities are just factoids. They look reasonable, but aren't proven. Like physical shock to a motor. Tested. Smaller BP motors are tough. The weakness turned out to be thermal cycling. I don't know that's true (problems proportional to impulse). There's more energy to make a bigger consequence. But I don't know about actual failure rate. Maybe there are factors that co-vary with impulse - like novelty of a new motor size (I'm using novelty as the inverse of experience), complexity of motor prep, go-fever, etc. that make it seem that way.